Unlike primary batteries which are not chargeable, chargeable and dischargeable secondary batteries are actively researched for applications to high-tech fields including digital cameras, cell phones, notebooks and hybrid vehicles.
Secondary batteries may be classified into nickel-cadmium batteries, nickel-metal hydride batteries, nickel-hydrogen batteries, lithium secondary batteries and the like. Of these, lithium secondary batteries are generally used in portable electronic equipment or high-power hybrid vehicles due to high driving voltage and excellent energy density per unit weight, as compared to nickel-cadmium batteries and nickel-metal hydride batteries.
Meanwhile, generally, a lithium secondary battery includes: an electrode assembly including a positive electrode, a negative electrode and a separator; electrode taps extending from the electrode assembly; electrode leads welded to the electrode taps and the like.
In this case, the negative electrode is generally formed by coating a current collector with a carbon-based negative electrode active material. In this case, in the prior art, crystalline carbon such as natural graphite or artificial graphite having a high theoretical limit capacity was generally used as the negative electrode active material.
However, natural graphite, artificial graphite or the like increases the viscosity of a negative electrode active material slurry over time due to high water absorption capability and causes problems of difficulty in controlling a predetermined load and thus remarkable deterioration in processability when electrodes are produced using the same.